1. Field of the Invention
The present invention relates to a low-frequency treatment device for medical use, in particular, for applying pulse waves to a living body so as to give an electric stimulus to muscles or the like.
2. Description of the Related Art
Conventionally, low-frequency treatment devices for applying pulse waves to a living body so as to give an electric stimulus to muscles or the like are widely known. In treatment using such a low frequency treatment device, electrodes are attached to a desired part of a living body, and a voltage having a low frequency such as a few Hz to a few hundred Hz is applied to the electrodes, so as to apply an electric stimulus to muscles of the living body. In a known technique, a plurality of pairs of electrodes are attached to a living body, and pulse signals having frequencies which are slightly different from each other are respectively applied to the pairs of electrodes, so as to generate interference waves between the pairs of the electrodes and to equivalently apply a low-frequency voltage to the living body. According to this technique, pulse signals are supplied to the pairs of electrodes from a plurality of oscillators for generating slightly different frequencies, by which low-frequency treatment by interference waves of a few Hz or the like can be easily performed. For example, by using electrodes which oscillate at 4000 Hz and electrodes which oscillate at 4010 Hz, interference waves having a frequency of 10 Hz can be easily generated in a living body (see, for example, Japanese Unexamined Patent Application, First Publication No. 2004-049651, in particular, paragraph Nos. 0018 to 0031, and FIGS. 1 to 5). In addition, the degree of fatigue in muscles may be measured and a low-frequency signal in accordance with the degree of fatigue may be applied to electrodes, thereby effectively stimulating a living body by the electrodes in accordance with the degree of fatigue in muscles (see, for example, Japanese Unexamined Patent Application, First Publication No. H11-253560, in particular, paragraph Nos. 0005 to 0022, and FIGS. 1 to 3). In another known technique, the amplitude of high-frequency carrier waves is modulated using low-frequency waves and the modulated wave signal is applied to electrodes, thereby stimulating from the surface to the deeper parts of a living body by the electrodes (see, for example, Japanese Unexamined Patent Application, First Publication No. 2003-010344, in particular, paragraph Nos. 0018 to 0033, and FIGS. 1 to 5).
In the above conventional low-frequency treatment devices, a time period for treatment can be set in consideration of an objective of treatment. When a preset time period for treatment has elapsed, the value counted by a timer has expired, so that the low-frequency treatment device may automatically stop the operation, or an alarm may ring so as to urge the user to manually stop the treatment device. For example, when the low-frequency treatment device is operated so as to subject a living body to an athletic training regimen with an objective of preventative medicine, the time when the timer has expired can be freely set in accordance with the age, sex, health conditions, or the like of a subject (i.e., a living body) by operating a dial knob provided on an operation face of the low-frequency treatment device. Therefore, when the user sets a desired time period by using the dial knob of the low-frequency treatment device, a voltage (or a current) of a low-frequency pulse signal is supplied to the electrodes only for the set time period, and an electric stimulus can be applied to neuromuscular parts of the living body.
However, when electrodes are attached to a specific part of a living body so as to intermittently apply a low-frequency pulse signal at specific intervals, it is known that the effects of treatment depend not on the treatment time period, but on the number of times of repetition of (a series of) conducting and pausing the pulse signal (i.e., the number of times of muscle contraction (i.e., contractile activity in muscles)). It is also known that determination of the number of times of repetition of conducting and pausing of the pulse signal in accordance with a mode relating to conducting and pausing of the pulse signal, a voltage or a current of the pulse signal, a muscle part to which the electric stimulus is applied, or the like, can produce optimum effects of treatment. However, in the currently-available low-frequency treatment devices, only a time period counted by a timer can be set, and it is impossible to set the most suitable number of times of repetition of conducting and pausing the pulse signal for each subject. Accordingly, the currently-available low-frequency treatment devices cannot produce optimum effects in treatment for each subject, and thus are not convenient.